glad to have you two aboard.
The standard upgrade path for an RSX is Intake, Header, Exhaust. Since she already has an intake and a muffler it's a good start. Getting a raceheader and full catback exhaust will definitely free some horses up. Though if you go raceheader you have to get engine mounts as well.
If you just want to chip it, there's really only one company... Hondata. There's two options. You can go with the ECU reflash which lowers your vtec engagement point, increases your redline, and optimizes cam timing for more power. It costs about $600. If you get a raceheader then I would recommend K-pro, which is the fully programable ECU. This is where you can really make some improvements. The thing that sucks though is that for the 05-06 you have to also buy an 02-04 ECU, which drives the price from $1,145 to $1,745. Though it will allow you to optimize your engine no matter what you add one to it (cams, turbo, supercharger, etc).
I buy most my parts from CRSX:
Club RSX.com
Hondata's website:
Hondata - Honda ECU Modification and Enhancement.
King Motorsports is another good website with plenty of fun toys to buy:
King Motorsports Unlimited, Inc.